Thermally actuated control device and circuit

ABSTRACT

A control device for setting the operating period for a motor useful in actuating a shoe buffer or similar appliance. The control device is a relay whose contacts are closed and opened as a consequence of the heating of a coil surrounding one of the bimetallic strips of the relay. The relay is so constructed that closure of the aforesaid contacts occurs substantially instantaneously, that is, in an extremely short time period upon application of current to the heating coil. Moreover, the relay is adapted to have the contacts return to the open state in a much longer time period; such longer time period constituting the operating period for the apparatus to be controlled.

United States Patent 1 Mello et a1.

m 3,760,317 [451 Sept. 18,1973

1 1 TIIERMALLY ACTUATED CONTROL DEVICE AND CIRCUIT [75] Inventors: Robert Edward Mello/Rockville;

' Armand Ciavatta, Meriden, both of Conn.

[73] Assignee: General Signal Corporation,

, Rochester, N.Y. 22 Filed:' Jan. 31, 1972 [21] Appl. No.: 221,887

s2 U.S.C1. 331/103 51 Int. Cl. 11011161/02 [58] Field of Search ..337/102,103,105

[56] References Cited 2 UNITED STATES'PATENTS 3,210,502 10/1965 Slonneger 337/105 2,914,637 11/1959 Wuerth 37/103 3,660,792 12/1970 Strain et a1. ..337/102 3,099,731 7/1963 Boddy ..337/102 1,830,578- 11/1931 Vaughan ..337/103 Primary Examiner-Harold Broome Attorney-John F.-Ohlandt "[571 I ABSTRACT A control device for setting the operating period for a motoruseful in actuating a shoe buffer or similar appliancei The control device is'a relay whosecontacts are closed and opened as a consequence of the heating of a coil surrounding one of the bi-metallic strips of the relay. The relay is so constructed that closure of the aforesaid contacts occurs substantially instantaneously, that is, in an extremely short time period uponapplication of current to the heating coil. Moreover, the relay is adapted to have the contacts return tothe open state in a much longer time period; suchlonger time period constituting the operating period for the apparatus to be controlled. l

2 Claims, 2 Drawing Figures PATENTEDSEP1 5mm POWER SOURCE FIG. 2

THERMALLY ACTUATED CONTROL DEVICE AND CIRCUIT BACKGROUND OBJECTS AND SUMMARY OF THE INVENTION The present invention pertains to a control device or relay and more particularly to a control. device which is thermally actuated for controlling the operation of a way by the features of the present invention. A primary feature resides in the provision of means forming part of the thermally actuated control device adapted to produce substantially instantaneous deflection of one of the bi-metal contact strips so as to effect operation of the relay contacts normally to cause them to close motor or the like. The invention also pertains to the ciryears for the purpose of controlling the operation of other devices in response to changes in temperature. One example is-the commonly used thermostat adapted to control the heating system in a home or the like. Such a device utilizes the differential expansion characteristics of a thermostatic bi-metal element for effecting closure or opening of contacts, thereby controlling in the desired fashion the given device or apparatus.

A very specialized device, also known in the art and involving thermostatic bi-metal elements for control purposes, is a time delay relay actuated by an electrical heating coil wound around one of the bi-metal elements, therelay including two such bi-metal elements for ambient temperature compensation- A specialized device of this sort can be appreciated by reference to the 1971 catalog of the W. M. Chase Co., 1630 Beard Avenue, Detroit, Mich. 48209 in which there is illustrated on page 29 such time delay relay. The purpose behind deployment of the two bi-metal elements is to prevent contact operation under conditions of changing ambient temperature. By'having both contact strips I composed of a bi-metal, it is insured that even though the ambient temperature changesthe' spacing between contact points will remain the same becausethe two'bimetalstrips will be deflected to the same extent.

However effacacious the prior art, time delay relay devices may be for their intended purposes, so far as is known such devices function in such a way that they are not adapted to effect contact operation substantiallyinstantaneously. By substantially instantaneously in this context is meant an extremely short time period of the order ofone second.

In contrast to prior art devices, the device of the present invention functions to produce immediate closure of its own contacts and hence, is adapted to be used in conjunction with a push button type of switch which provides only momentary closure of its contacts. In other words, the push-button switch effects connection of the-appliance to the power source only briefly, that is, for a time period of the order of one second; but, by the closure of its own cOntacts, the device of the present invention is able to keep the power source connected to the appliance for periods up to three minutes.

Accordingly, it is a-primary objectof the present invention to provide a thermally actuated control device and circuit capable ot effectuating contact operatic in 'an extremely short time period.

A related object is to immediately short circuit the in an extremely short time period. The preferred form that this means takes is a low resistance for the heating coil which is wound about the one bi-metal contact strip.

As a result, when power is applied to the low resistance heating coil, it heats up very rapidly, causing substantially instantaneous deflection of the contact strip and consequently, in the usual case, producing closure of the relay contacts. The heating coil is so connected to the one contact strip that when closure of the contacts is effected, the heating coil is shunted so that it no longer draws current and, therefore, begins to cool off. The cooling off period for the coil determines the on" time for the appliance or apparatus being controlled. Moreover, this closure of the aforesaid contacts, which produces the shunting of the heating coil, alsoinsures continuation of the appliance in the on" state for the cooling off period.

The time period which is consumed in the cooling off of the heating coil is of extended duration when compared with the extremely short time period in the initiation process, i.e., in closing the relay contacts and turning on the appliance. A typical time period for cooling down of the heating coil and, hence, for apparatusoperation is of the order of a hundred seconds.

Other objects, features and advantages of the present invention may be appreciated by reference to the following description, taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION: OF DRAWING.

FIG. 1 is a perspective view of the thermally actuated control device of the present invention. v 1

FIG. 2 is a schematic diagram of a circuit in which the control device may be incorporated.

' DESCRIPTION or PREFERRED EMBODIMENT cuit connecting'purposes as will be explained. Al-

its secured end to appropriate terminals 18 and 20, re-- spectively. The bottom strip, 16, has no electrical connectionthereto. Its purpose is to function to adjust the position of the contact strip 14 by means of a setscrew 22 set in a suitably threaded aperture in the strip 16. Adjustment of the setscrew results in moving the strip and, therefore, in varying the spacing between the juxtaposed spaced contacts 24 and 26 disposed at the fre ends of the contact strips 12 and 14, respectively.

The uppermost strip 12 is surrounded by an electrical heating coil 30. Power is supplied to the coil 30 by means of the terminal 32 which is part of the stacked group of terminals bolted together at the secured end of the contact strips. The terminal 32.is connected to one end of the coil 30 by a suitable wire lead 33. The coil 30 is insulated throughout the extent of its encirclement of the contact strip 12 by means of an insulator material 34 wrapped around the strip 12. Theopposite end of the coil 30 is electrically connected to the strip 12 by means of a solder contact 35 or the like, whereby the strip 12 serves as a return path for current from coil 30 to terminal 18.

The typical operation of the control device of the present invention in 'a circuit environment can be appreciated by reference to FIG. 2. In this embodiment a power source 40 of l volts is to be applied to a utilization device in the form of a motor 42. The arrangement is such that the motor operation will be effectuated over along period of time of the order of a hundred seconds, by reason of employment of the control device 10. The control device 10 is shown in the dotted-line box. Within the dotted box, and identified by the same numerals as in FIG. 1, are the parts of the control device 10. The control device serves to connect the power source 40 to the motor 42 through the convenient medium of a push-button switch 44 which is energized by the user on a momentary basis. That is, the user actuates the push-button and suitably arranged contacts 44a are closed for a brief interval of the order of one second. As a result of such momentary actuation, curren is permitted to flow by way of terminal 32 on the control device 10 through the heating coil 30. The characteristics of the coil are such that it heats very quickly, its resistance being chosen in this preferred embodiment to be of the order of 21 ohms. Thus a current of approximately 1.7 amperes flows, after an initial transient period, through the coil 30.

Immediately upon being heated sufficiently, which occurs in one second, the contact strip 12 around which heating coil 30 is wound is caused to deflect, thereby producing, in this embodiment, closure of the contact 24 against the contact 26. As a result, power is now supplied through these closed contacts directly to the motor 42 and at the same time, the heating coil 30 is shunted.

The motor 42 is consequently energized for its desired purpose. Typically the motor 42 would be embodied in a shoe buffer mechanism. During the period of the motors energization, no current is being supplied through the heating coil 30 for the reasons noted. Motor 42 will continue to operate until the heating coil 30has cooled off sufficiently such that contacts 24 and 26 return to their former state, that is, to the open state, thereby turning off the motor 42.

What is claimed is:

1. In a circuit for connecting a power source for a predetermined time period to a utilization device, the combination comprising:

1. a pushbutton switch adapted to provide momentary connection of said power source to said utilization device;

2. a thermally actuated control device connected to said pushbutton switch and to said utilization device, said control device comprising:

a. a pair of contact strips having juxtaposed contacts capable of being closed, at least one of said strips being composed of a bi-metal;

b. a heating coil wound around said one strip to produce instantaneous deflection of said one strip, upon application of power to said coil, so as to effect closure of said contacts in an extremely short time period of not more than one second, and further adapted to open said contacts, upon removal of power from said coil, after a much longer time period, said heating coil being series connected to said pushbutton switch and said utilization device;

c. means including said contacts short-circuiting said heating coil and said pushbutton switch responsive to closure of said contacts so as to remove power from said coil.

2. A device as defined in claim 1, further including first, second and third terminals,

said coil being connected at one end to said first terminal and at the other end to said second terminal;

said one contact strip of said pair being connected to said second terminal, and the other contact strip being connected to said third terminal.

l l i 

1. In a circuit for connecting a power source for a predetermined time period to a utilization device, the combination comprising:
 1. a pushbutton switch adapted to provide momentary connection of said power source to said utilization device;
 2. a thermally actuated control device connected to said pushbutton switch and to said utilization device, said control device comprising: a. a pair of contact strips having juxtaposed contacts capable of being closed, at least one of said strips being composed of a bi-metal; b. a heating coil wound around said one strip to produce instantaneous deflection of said one strip, upon application of power to said coil, so as to effect closure of said contacts in an extremely short time period of not more than one second, and further adapted to open said contacts, upon removal of power from said coil, after a much longer time period, said heating coil being series connected to said pushbUtton switch and said utilization device; c. means including said contacts short-circuiting said heating coil and said pushbutton switch responsive to closure of said contacts so as to remove power from said coil.
 2. a thermally actuated control device connected to said pushbutton switch and to said utilization device, said control device comprising: a. a pair of contact strips having juxtaposed contacts capable of being closed, at least one of said strips being composed of a bi-metal; b. a heating coil wound around said one strip to produce instantaneous deflection of said one strip, upon application of power to said coil, so as to effect closure of said contacts in an extremely short time period of not more than one second, and further adapted to open said contacts, upon removal of power from said coil, after a much longer time period, said heating coil being series connected to said pushbUtton switch and said utilization device; c. means including said contacts short-circuiting said heating coil and said pushbutton switch responsive to closure of said contacts so as to remove power from said coil.
 2. A device as defined in claim 1, further including first, second and third terminals, said coil being connected at one end to said first terminal and at the other end to said second terminal; said one contact strip of said pair being connected to said second terminal, and the other contact strip being connected to said third terminal. 